The present invention relates to a pod unit comprising a pod housing with a steering engine, a fan system, a slip-ring device, and an assembly unit, so called seating, for the pod housing, the seating being a portion of the hull bottom and comprising a base for the mounting of said pod housing, which comprises a lower casing portion intended to accommodate a propulsion unit, an intermediate portion comprising air ducts and an upper portion, which is fixedly connected to a steering engine having a gear ring to be fixed at said base.
The pod system has become a more and more common alternative for the propulsion of marine vessels. The advantages as compared with conventional systems are: shorter time of installation; possibilities of simpler and more flexible maintenance as well as possibilities of a quick exchange of the entire propulsion unit. Known pod systems, however, show certain drawbacks. Such a drawback is that the delivery unit/module for the pod system itself and the fan system for cooling of the pod engine according to the technique known today is divided, which may imply certain complications in connection with the assembly, as both these systems must be carefully adapted to each other and mounted in a special sequence. According to known technique, the seating is first welded to the hull, and then the steering engine can be mounted. Thereafter, the pod housing may be mounted and only thereafter the slip-ring device and the fan system may be mounted. Further, the fan system according to known technique is mounted at a level above the hull bottom, which implies that the cooling effect from the water against the hull bottom cannot be utilized. It is realised that a better cooling effect of the air should lead to savings in the form of less power requirements for the cooling.
Another essential drawback with today""s pod systems is the comparatively high costs. These costs depend among other things on the plurality of components as well as the comparatively bulky installation requirements of the system. The assembly can often be comparatively complicated because of the fact that great accuracy is required for the installation of the pod unit at the hull. The rotatable portion of the pod unit is provided in a box-shaped assembly unit, a so called xe2x80x9cseatingxe2x80x9d, which consists of a module element which is welded to the hull and which also aims at transmitting the cargo from the pod housing to the hull. There is a risk that said seating, because of the welding, may buckle, which in turn implies that a machining of the base for the installation of the pod unit must be made. Such subsequent machining is complicated and expensive and therefore not desirable.
Additionally, today a steering cone, which is provided through the seating, is used for the steering of the rotation of the pod unit, which in itself is an expensive construction.
The object of the present invention is to eliminate or at least to minimize at least some of the above mentioned problems , which is achieved by a cooling system comprising at least one fan mounted within the seating.
With this solution, a pod system is obtained, wherein the pod housing with the steering engine is a delivery unit, which is compact, has a low building height and implies a lower cost than conventional systems. Due to the fact that the seating with the cooling equipment and the pod housing with the steering engine can be delivered as controlled and tested units a simpler, cheaper and safer installation with the shipyards is obtained. Further advantages of the invention according to the preferred embodiment are that a better cooling efficiency is obtained, as the air flow runs in the seating with direct contact with the plates adjacent to the water.
According to further aspects:
the upper edge (14B) of said gear ring (14) is provided near the lower portion (6A) of the seating, the distance between said upper edge (14B) and the shortest distance (X) to the imaginary hull line (L) of the seating being below 900 mm;
at least one cooling unit is installed within said seating;
a drum (29), which is installed inside the seating and which is preferably provided coaxially to and above said base (15), has an inlet opening (23) and an outlet opening (22), respectively, for cooling air;
the seating (6) comprises side walls (6B, 6C, 6D, 6E), and stays (21) provided with holes (21A) are arranged between said drum (29) and said side walls (6B-6E), said stays transmitting cargo and also enabling transport of air;
an assembly flange (16) intended to connect said base (15) to a bearing socket (19) for the gear ring (14) which is intended to be connected to the upper portion (4C) of the pod housing;
said gear ring (14) is arranged with the cogs on the inside thereof;
a base is provided nearer the lower portion (6A) of the seating than the upper portion (6F) of the seating; and
said distance (X) is between 0.1 and 0.2xc3x97 the diameter (D) of the gear ring (14).